Continuous pouring of metals



Nov. 18, 1969 M. LAFFIN 3,478,814

CONTINUOUS POURING OF METALS Filed June 22, 1967 INVENTOR MICHEL LAFFINI: My, BMAMLQZLMM 3 HIS ATTORN EYS United States Patent 3,478,814CONTINUOUS POURING OF METALS Michel Laflin, Annecy, France, assignor toSociete Anonyme: Ugine Kuhlmann, Paris, France, a corporation of FranceFiled June 22, 1967, Ser. No. 648,097 Claims priority, applicationFrance, June 24, 1966,

Int. Cl. 1522a 15/02 US. Cl. 164281 2 Claims ABSTRACT OF THE DISCLOSUREVarious methods and devices are known and generally used for thecontinuous pouring of hollow metal bodies. Amongst other devices one hasbeen described for the continuous horizontal pouring of metal pipes,such as aluminum-tin pipes, in which a stationary mandrel with aslightly tapered head is positioned at the entrance of the chill mold.Now, it has been established that by operating in accordance with thesemethods, or with these known devices, continuous pouring of a thickwalled pipe or solid rod is relatively easy, but for pouring thinwalledpipes difiiculties arise which render the method useless in practice.

Study of the phenomena has shown that these last difficulties ariseessentially at the beginning of the pouring operation; in continuouspouring of a thin-walled tubular product, blocking of the apparatus bysolidification of the metal before continuous pouring conditions areestablished is often seen at the beginning of the operation owing to thesmall cross-section of the product. Such incidents by reason of the costof repairs and immobilization of material, as Well as the loss of metaland production they entail, are all the more irksome as their occurrenceis as frequent as they are irregular.

The manufacture of thin-walled metal pipes is sufficiently important forit to have been the subject of efforts, which have been unsuccessful upto now, to overcome the serious drawbacks inherent in the known methods.As it is essential that the manufacture should not be burdened withadditional expense, efforts were deliberately directed to providing assimple a means as possible and preferably adaptable to known apparatusto permit thin-Walled pipes to be manufactured by continuous, and moreespecially horizontal pouring. Having posed the primary problem ofsimplicity and efiiciency, the applicant was surprised to ascertain thatall the aforesaid drawbacks could be eliminated and that the advantagesof continuous, and more particularly horizontal, pouring of solid rodsand thick-walled pipes were retained for thin-walled pipes when, inorder to pour thin-walled pipes, the poured metal was forced to takeprogressively the desired final internal section of the product. Thisresult can generally be obtained with a mandrel having a generallytapered shape and which is moved in the inlet of the chill moldaccording to the axis of pouring from an initial rearward position.

According to the invention, the method of continuous till 3,478,814-Patented Nov. 18, 1969 pouring, particularly horizontal pouring, ofmetal pipes, especially thin-walled pipes, by means of a chill moldcomprising a mandrel at the molten metal inlet, is characterized by thefact that the mandrel is moved along the pouring axis from upstream andwithin the poured metal so as progressively to attain the desired valueof the" inner section of the poured article, the intersection of thefront surface of solidification and the mandrel surface defining theinner section of the poured tubular article. This intersection isreferred to as the active section of the mandrel. Pouring can be startedin solid cross section and pass progressively to the tubular article,pouring can also be started with a small diameter hollow inner section.

It is possible, for instance, to pour first a solid member, then from apredetermined rear position and up to a front position alsopredetermined as a function of the nature of the metal and thecharacteristics of the size ofthe pipe to be obtained, to advance themandrel progressively and without stopping until the desired innersection and wall thickness is obtained. At the start of the operationthe mandrel is maintained in a position on the pouring axis such that atfirst, and until stable operation is established, a thicker wall thandesired is obtained and the mandrel is then moved forward until thefinal thin wall is obtained. At least the extreme rearward position ofthe front point or apex of the mandrel is upstream of the extremerearward position of the solidification face of the metal; thiscorresponding to solid section pouring. In the forward position of themandrel the largest crosssection of the mandrel, which is at its rearportion, is upstream of the extreme forward solidification faceposition.

The method according to the invention can be used at the start ofcontinuous pouring of hollow products, especially those with thin walls,it can also be used to pass without interrupting pouring from one typeof product to another; for instance, from a pipe of given wall thicknessto a pipe of another wall thickness. The new method therefore eliminatesthe drawbacks of anterior methods, especially all risk of untimelysolidification during the first moments of the operation; owing to thisfact it provided important industrial advantages in the manufacture andquality of products. One of these advantages lies in the possibility ofsubstantially reducing the production tolerances of the tubular articlesproduced, as the method permits the inner section of the poured productto be adjusted or controlled without stopping the continuous pouringoperation, by very slight movements of the mandrel for instance.

Another object of the invention is an apparatus for putting theinvention into effect. Such an apparatus comprising molten metal feedmeans; a coolable chill mold; means for extracting the poured articleand a mandrel having a tapering head penetrating the chill mold, ischaracterized by the fact that it is provided with means permitting thesaid mandrel and the solidification face of the poured metal to bedisplaced longitudinally with respect to each other. For example, theinstallation can be characterized by the fact that it is provided withmeans for moving the mandrel along the axis of the, chill mold withinthe poured metal and that the head of the mandrel has a sectionincreasing continuously from the downstream to the upstream end. Thehead of the mandrel can be conical with a rounded head situateddownstream; the mandrel head can also have a curvilinear surface Whosetangents are all inclined in the same direction with respect to the axisof the chill mold.

In the case of an aluminum-tin alloy, or alloys having similarmechanical properties, it is advantageous that the generatrices of theconical mandrel should have a slope of about 7 in the solidificationface zone. For other metals or alloys it is easy in each case todetermine the value to give the said slope after a few trials. The rateof development of the section of the mandrel should correspond to aslope of the generatrix of the cone which does not depart from thatproviding an inner skin of the poured product which is .acceptable tothe extent of leading to the rupture of this skin, and therefore to thefailure of the pouring operation. In the aforesaid case of aluminum-tinalloys and the like it is advantageous to use cones whose half angle atthe summit is between about 15 and 20.

In the appended drawing an example of embodiment of an installation isshown for carrying the method according to the invention into effect, Inthe drawing:

FIG. 1 is a diagrammatical longitudinal cross-sectional view of ahorizontal continuous pouring apparatus according to the invention;

FIG. 2 is a similar view to FIGURE 1 but for another position of themandrel.

In the drawing there is seen the container 2 which receives the moltenmetal 1 from a pouring ladle or similar one (not shown). The container2, lagged with a suitable insulating material 4, is sealingly mounted onthe pouring head 3, also thermo-lagged, with which it communicates by anorifice 5. In the pouring head 3 is secured, by any known sealing means,the horizontal chill mold 6 provided with a cooling jacket 8 pierced byholes 8' through which jets of cooling water can spout. On the otherside of head 3 is sealingly mounted a sleeve 12 within which isslidingly mounted in a sealed manner the stem 10 surrounded with athermoinsulating material 11 along a length substantially equal to thatof its possible movement; the downstream or front end of the stem 10 issecured in any known way to conical head 9 of the mandrel. Thelongitudinal displacement of stem 10 is controlled by a screw 13 drivenin rotation by crank 14.

The operation of this installation is as follows: initially the head ofmandrel 9 is in the extreme rear position shown in FIGURE 1; as themolten metal 1 passes from the container 2 into chill mold 6 throughorifice of the pouring head 3 it surrounds the rear end of the conicalhead 9. In response to the effect of the jets of water issuing throughorifices 8 of the jacket 8, the metal 1 cools and a solid bar 15 isobtained from the solidification face 7 of the metal.

As soon as the metal is flowing evenly the crank 14 is activated todisplace the stem and head 9 of the mandrel progressively downstream theend 9' of the head has just passed beyond the solidification face 7 anda pipe 16 is then obtained whose wall-thickness is determined by theposition of the intersection between the solidification face 7 and theactive surface of the head, i.e. the portion of the surface of the headupstream of which the metal is still molten. As the molten metal 1continues to arrive the article formed is a tube with a wall of thedesired thickness, without it having been necessary in practice to movethe head 9 to any extent.

The movement of the mandrel by the control screw is adjusted as afunction of requirements and according to the measurements carried outon the poured product, to keep the solidification face preferably in asubstantially fixed position in the chill mold. This adjustment can, ofcourse, be carried out automatically by suitable measuring and controldevices. Finally, it should be noted .4 that, if necessary, modificationof the cooling operation permits the position of this solidificationface to be modified.

What we claim is:

1. A device for the continuous pouring of metal shapes, from bars totubes having thin walls, comprising a container for liquid metal, on theinner wall of the container a layer of thermoinsulating material, alatreally thermoinsulated opening in the container for discharge of theliquid metal, a pouring head sealing surrounding said opening and havinga rear wall and a front wall, each wall with an opening therethroughboth openings having a common axis, the inside of said head beingprovided with thermoinsulating material traversed by channels coaxialand respectively communicating with the opening in the rear and frontwalls of the pouring head, a horizontal chill mold having a crosssection approximately that of the metal shape, said chill mold having anoutlet for the metal shape and a rear part tightly surrounding the saidfront opening of the pouring head, an annular jacket for cooling watersurrounding the peripheral outlet zone of the chill mold, holes in saidjacket which are directed to project water on the outer face of theoutlet of the chill mold and of the metal shapes, a sleeve tightlyfitted at one end around the rear opening of the pouring head, adetachable rear end at the other end of the sleeve the rear and frontopenings of the pouring head and the chill mold having said common axis,in the sleeve an axially movable unit consisting of a metal stem and ofa thermoinsulating material surrounding the stem and having an outerdiameter equal to the common inner diameters of the sleeve and of theopening in the rear wall of the pouring head, means to displace axiallysaid unit between a rear and a front position, a mandrel fitted on theinner end of the stem, said mandrel in the rear position of said unithaving at least a part of its apex portion in the chill mold and itsrear end applied both to the radial end surface of the insulatingmaterial of the unit :and to an annular portion of the inner surface ofthe insulating material in the pouring head around its rear opening, andsaid mandrel in the front position of said unit having its apex portionin about the vicinity of the outlet section of the chill mold.

2. A device according to claim 1, for the pouring of aluminum tinalloys, in which the mandrel surface is generally conical and thegenerators of the mandrel surface are inclined at about 7 to the axis ofthe chill mold, in the zone corresponding to the solidified metal limitin said mold.

References Cited UNITED STATES PATENTS 2,996,771 8/1961 Armand et al164283 3,228,075 1/ 1966 Lindemann 16485 3,398,780 8/1968 Yearley 16483X FOREIGN PATENTS 580,845 8/ 1959 Canada. 869,104 5/ 1961 Great Britain.

J. SPENCER OVERHOLSTER, Primary Examiner R. S. ANNEAR, AssistantExaminer US. Cl. X.R. 164-85

